Page:Memoir of a tour to northern Mexico.djvu/9

Rh late in the night at Camp Osage, (16 miles,) the first camp near the Arkansas. To-day we saw signs of the buffalo, and the first prairie dog village.

June 5.–Along the Arkansas, about two miles north of the river, we marched eight miles, up to Walnut creek, another of its tributaries, to make our usual noon halt. On the road we met with the first buffaloes, in small bands, but they were too wild for us to approach them. Half way on our morning march, about three miles north of the Arkansas, there is a slight chain of hills in the prairie, mostly overgrown with grass. Attracted by a prairie grave on this elevation, made of a heap of rocks, I was astonished to find these rocks not to be lime or sandstone, but to resemble a volcanic formation; and upon further examination, I discovered the same rock in situ, cropping out at the southern end of the hill: the rock is a porous, red, black, and yellow mass, as if earthy substances containing iron had been baked together by strong fire. It shows great similarity to the burnt rocks in the cretaceous formation on the upper Missouri, specimens of which the late Mr. Nicollet brought back from his expedition; but the latter are blacker and lighter. The character of the rock, as well as of the surrounding country, excludes the idea that it was thrown up from the depths by volcanic action; but it is more likely that it was produced by pseudo-volcanic fires, or subterraneous fires near the surface, ("Erdbraende," as the German geologists call it,) such as are generally called forth by spontaneous or accidental ignition of underlying coalfields. When, in the evening of the same day, I found the same formation again on Pawnee Rock, it was in so intimate connexion with the ferruginous sandstone that it left no doubt in my mind that this scoriaceous rock is the product of action of such fires upon the ferruginous sandstone.

In the afternoon we started again for Ash creek, (19 miles.) Our road went through a sandy plain, with short and fine grass, the so-called buffalo grass, (Sessleria dactyloides;) the Arkansas river running a few miles south of the road. The whole plain through which we passed was really covered with bands of buffaloes; their number must have been at least 30,000. The hunting fever soon became epidemic; all rifles and pistols were put into action, but the huge animals were more frightened than injured. The level of the plain did not allow us to take them by surrounding, and only the hunters, who chased them on fast horses, had the good fortune to kill any. About six miles east of Ash creek there is a prominent rock seen to the right of the road, connected with a small chain of hills, and known under the